Evap & EGR Issues

[Azash]

I have a 2001 5.3 and I'm getting a P0404, 405, 449, and 453. Mechanic friends have told me this is probably the vent valve. I've been told the best test for this is a fog test, but I'd like to hear a few more opinions before I take it to get tested. It's also got a P0300, random misfire, which I believe is the result of these other problems. I'd like to get this fixed to I can actually burn the fuel I'm buying instead of dumping it out my exhaust.

 

[Azash]

I'm now also getting a P0446, saying my vent control circuit is malfunctioning. # of these codes point directly at a bad vent valve, but there's 2 that point at an EGR which I believe I just replaced last summer, is it possible this has gone bad already or is it more likely a result of these other codes?
Also since no one's giving their opinion on these codes, can anyone give me facts about replacing the vent valve? Anyone here done it before? Any problems I may run into or certain procedures (ie depressurizing fuel system)?

 

[rockenthebowtie]

Dont need to depressurize the P0449 is evap vent valve control circuit failure very common its an internal failure its pretty much plug and play.. the P0453 is the fuel tank pressure senor and can be related to the P0449.. the EGR Code is that the EGR pintal isnt seating all the way and can cause the P0300... remove the EGR Valve turn it upside down and see If anything is caught between the pintal and housing of the EGR Valve

 

[rockenthebowtie]

Also quit being so inpatient not everyone here may know whats going on or those that do may not be logged on lol

 

[Azash]

Hey, thanks a lot! Now I have somewhere I can start from. When you're talking about the 0449 and say it's plug and play are you saying I need an electrical component or just unbolt the old and in with the new? I just got a quote on a vent valve today for like $35 from the dealer, but if it's something else I'd want to know. Any info on location of the vent valve would be helpful. I'm not really a mechanic but I know how nuts, bolts, and clips all work. If I know the part and location I can take care of it myself, I just don't currently know what part and location I need to get into. And my apologies, I wasn't being impatient, it kinda does seem that way rereading it now though. It was more along the lines of if you can't guess at this, give me any actual info you may have, even if it's small. I know my vehicle doesn't take presidence over other peoples lives so I'm not trying to be pushy, I'd just like my mpg back up above 13 is all.
On a side note if I do have to replace the vent valve, should I do the vapor canister too or can that be another project for another time? I'm only asking that because one person mentioned that if I'm doing one, I should do the other. If this has nothing to do with my current problems then I'm not going to touch it seeing as though the canister is $200.
Again thank you for any input.

 

[rockenthebowtie]

I was just messing with you bro... the vent valve should be at the right side of the fuel tank towards the front of vehicle... it has a red and light blue electrical connector with a black plastic hose connected to it... no dont need to change out the charcoal canister just yet...

 

[Azash]

So don't change the canister if it doesn't need it? The truck has 183k on it if that makes a difference. I also had someone dump diesel or oil into my tank a few years ago, so it's got a new (to my truck, off of a silverado I believe) tank and pump. I don't know about the rest of the stuff though like the canister.

 

[rockenthebowtie]

Well just start with the solenoid for now and see how it goes

 

[Azash]

Well I took out the EGR valve last night and it was pretty clean, not too much build-up and nothing blocking it's movement. This mean the EGR valve itself is bad? I'll be doing the vent valve this weekend and see if that fixes the rest of the issues. Is it possible the EGR codes are being thrown because of things caused by the bad vent valve? I guess we'll see...

 

[rockenthebowtie]

No egr and vent solenoid are on 2 different control circuits.. maybe a bad egr valve or connector

 

[Azash]

Ok cool, I found a guide for testing my type of EGR for most any issues (P0401, P0403, P0404, P0405, P1404, AND P1406). For anyone with the same EGR valve that guide is at http://easyautodiagnostics.com/gm_egr_test/gm_egr_valve_1.php. The only thing you need for his tests is a multimeter, which a lot of people have, otherwise he's got a link to his suggested ones if you do not.
So I'll be pulling that back off and performing all those tests to make sure it's actually bad. Seeing as though it's about $150 for a stock replacement, I don't just wanna replace it willy nilly, I'm just glad it's REALLY easy to get to and test.

 

[Azash]

Well over the weekend i replaced the vent valve and the EGR valve. I still have the P0300 (random misfire), 405 (EGR sensor A circuit low), 452 (evap emission pressure sensor switch low), 453 (evap emissions pressure sensor high). The last two are contradictory which really leaves me confused. Both can come from a bad FTP sensor, so I bought one of those, I just haven't put it in yet. So if anyone knows where exactly that is you'll save me a flip through my Haynes. This still leaves me with a malfunctioning EGR system. As I said I put a new EGR in so I was really hoping that would fix the EGR problems. But if you know what else could trip that code, please let me know.

 

[rockenthebowtie]

Ok for the EGR issue I did mention that you might have a bad connector the brown wire is the one that sends the egr pintal position to the computer so either you have an open in that circuit from the egr valve to the computer or connection at the egr valve itself or at the computer... my guess it's going to be at the egr valve.. you can get a pigtail connector at the dealer not sure if you can get one at any local auto parts store... as far as the FTP sensor that sits at top of the fuel pump assy so you have to drop the gas tank only there maybe an open and or short in the 5 volt reference circuit which is the gray wire so your going to need a volt ohm meter with the key on the gray wire should have no less then 4.5 volts to it so you need to disconnect the ftp sensor and check that voltage right at the connector

 

[Azash]

Well a few weekends ago I put in a new EGR valve, vapor canister (found out one of the nipples coming out of it was busted, don't know if I did it trying to drop the tank or if it was already busted), and the FTP sensor. I still have the random misfire and P0404 code for a bad EGR. I was testing with my multimeter when I found out it's a piece of chinese crap. My father's an electrical engineer so I'll be taking it by him and having him check my EGR voltages to see what's going on with that now. I just checked and now I also have a P0442, small leak in the evap system. Any advice as to what that could be now? I'm going to check all the stuff I had to disconnect to drop the tank, but could it be anything else?

 

[Azash]

My tahoe also has the "vortec tick", I belive that's what I've seen it referred to as. Could that be related in any way? And what causes it to tick like that? It's just a small knocking sound that goes away after a few mins at idle or about 1/8 mile if I start driving right after start up.

 

[Azash]

ok so it's been a while since i updated. i took the truck to a mechanic now. he told me the NEW egr valve i got from advanced was a frickin dud so i had to get another one, this time from carquest. he said it's throwing some other codes that are probably related to this, but it's also still showing a leak in my evap system somewhere even after i replaced the canister. i had to spliced in a new fuel filter and in doing so i apparently over tightened one of the nuts so it got a leak and was dripping some gas. could this be that leak in the evap or is it unrelated? He also said the misfire was mostly happening at idle, said it could be because my injectors could have some crud on them and told me to put some techron in my tank. so i did that this morning. will update after all this is sorted out in hopes it can help someone else as this was all kinda boggling for me.
on a side note the cable to my rear pass brakes for the pbreak busted the other day. i just ziptied the wire off to the side since i haven't used the pbreak the whole time i've had the truck. and i also just had to replace the ujoints. i got a vehicle inspection, troubleshooting for the codes and the ujoint work done at a Craigs in west bend wi for $240.09. he took me under the truck and showed me everything going on with it he could and they're all nice, intelligent, reasonable people and i would recommend this garage to anyone.

 

[rockenthebowtie]

Well lets see if this works... you've already replaced the egr valve.. what 2 to 3 times already and still the same issue Right ? Now do you really think that all of those egr valves could really be defective ooooorrr is it possible that the harness connector could be the problem.. I think I may have suggested that oh 2 or 3 times... do this disconnect the egr valve connector and drive the truck to see if the misfire goes away if it does you may have a shorted control circuit and or bad pcm

 

[Azash]

Well the mechanic had one of those really fancy computers they hook up to the truck and said it was actually the egr. I had the 1st one i bought in there when i took it in, he said it wasn't reading what it was supposed to. i told him he could double check with my original which i still had in my truck. he did that and told me that one was reading nothing and was totally shot. so i bought a new one and he installed that, said all the voltages and stuff were spot on.
now i'm not trying to go against your advice, (especially seeing how helpful you've been so far!) but his logic on the misfire did seem pretty good to me. he said whilst at idle it was basically dripping into my cylinders because of some buildup, so not atomizing and not firing correctly. but when you hit the accelerator it ups the psi and volume of fuel going into the cylinder, causing it to perform better.
that night i put some techron in, but considering how much fuel was leaking from my line that day a lot of it probably didn't get in there. that was last friday. i fixed the fuel leak monday night and then put some more techron in. it does seem to be running more smoothly and the misfires seem fewer and not vibrating the truck as much.
i have a 17mi drive home, so i'll try disconnecting the egr harness before i go home tonight and see if it starts misfiring like it did 2 weeks ago.
Thank you again for all the help and advice!

 

[rockenthebowtie]

ey bro your very very welcome guys like you are why I continue to do my best to help out here I really do like your words of appreciation... so anyway the reason I stress the harness connector is it is recommended to replace when replacing the egr valve if you were to unravel the lomb and tape around 6 to 8 inches from the connector you will see that from the heat the insulation is stuck and melted together that can and eventually start shorting out together and cause the egr to malfunction such as open at idle and causing a misfire now I'm not saying it doesn't happen buy its rare for that type designed injectors to get plugged up and cause a misfire like that if that mechanic has that type of scan tool ask him if he can look at misfire data and if so look to see what cylinder is misfiring and pull the plug on that cylinder to see if its carbon up( black ) all on the porcelain if so there would be the bad injector..

 

[Azash]

I was there for a while with him looking at it. It really was random, after a minute there were like 10 misfires on cyl 6, 7 on 3, 4 on 4, etc. Those aren't exact, but it was something like that. Plugs are easy enough to check (except the back one facing the firewall, that one's a pita), i guess they're getting kinda old, maybe 5 years tops. i did buy the platinum ones and at the same time put the higher performance wires on too, but stuff goes bad. That wiring should be easy enough to check too, so i'll take a look at that. do you happen to know if i can get the connector at a parts store, or is that a dealer part? also is there a recommended heat tape i can wrap around it once i've unwrapped it (whether or not it's damaged). And if so, is there anything else i should wrap while i'm at it?